JPS5742291A - Individual callout system for digital discussion line - Google Patents

Abstract

PURPOSE:To make unnecessary a hybrid circuit and a filter and to obtain an individual callout circuit with a simple circuit constitution, by realizing an individual callout of a discussion telephone system in a digital line through the use of required number of different PN patterns. CONSTITUTION:A gate switching signal from an input terminal 5 is inputted to a PN pattern generating circuit 1, and PN pattern signals are generated with this switching signal, and they are inputted to a signal switching circuit 3 taking the output from a digital code circuit 2 as input. The PN pattern signals assigned to each station from the switching circuit 3 are transmitted to a transmission line. The PN pattern signal is detected at a PN pattern detection circuit 7 at reception station side, and the exclusive logical sum between the PN pattern of the station itself and the received PN pattern is taken as a gate 6 of logical sum. The output pulse of the gate 6 is counted at an error pulse count circuit 10. When the count valve in unit time of the circuit 10 is less than a given value, it is judged that the station itself is called out and audio signals from the circuit 3 are transmitted for the time other than the callout time.